Fwiw, once upon a time a fan asked him if the Eternal Silence statue was letting Alfred communicate because it's materials were originally sourced on Demonreach (the questioner mistakenly thought the statue was stone rather than bronze). Jim said something to the effect that would have been a really cool idea, but by that point it was already written into the books that Mab had been facilitating that communication. So while there's nothing cannon in that, it gave me the impression that he views it as a reasonable mechanic, and Id say it's entirely consistent with what we know of Thaumaturgy in general. It likely wouldnt let him tap the Ley Line or expand his Intellectus past the island or anything, but communication shouldnt be a problem. Worst case you build a radio-style paired receiver system; if one side is on the island it is within Alfred's sphere of knowledge, and now that he'd getting more skilled at Languages he should be able to use such a device (might still need a SoI translator, be we know of some)